Engine protective device



' M; HQO'BRIEN Er AL July 14, 1959- ENGINE PROTECTIVE Davies 2 Sheets-Sheet 1 Filed Sept. 7, 1956 July 14, 1959 7 M. H. O'BRIEN ETAL 2,894,502

' ENGINE PROTECTIVE DEVICE- Q Filed Sept. 7, 1956 2 Sheets-Sheet 2 United States Patent ENGINE PROTECTIVE DEVICE Michael H. OBrien, Detroit, and Roger D. Wellington,

Birmingham, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 7, 1956, Serial No. 608,470 15 Claims. (Cl. 123-198) This invention relates to devices for protecting internal combustion and other types of engines against continued operation in the event of a failure of certain essential accessory systems, such as a failure of their cooling or lubrication systems, as well as against excessive engine speed developing for any reason in operation.

Among the principal objects of the present invention are to provide an improved safety shutdown or protective device for such engines; to provide such a protective device with a condition responsive means including means for modulating'the condition response of said responsive means in accordance with the speed of the engine; to provide such a protective device with a condition sensitive means including a release mechanism and means for modulating the datum of the condition at which said release mechanism is actuated in accordance with the speed of the engine; to provide an oil pressure sensitive means for such a protective device with a pressure release mechanism operative in response to a drop in the engine lubricating oil pressure below the safe operating pressure for a particular engine speed or in response to excessive engine speed to simulate a failure of the engine lubricating oil pressure; and to provide such a protective device with an improved speed responsivemeans for simulating such a failure of the engine lubricating oil pressure including means for modulating its speed responsive action in accordance with the lubricating oil pressure.

The foregoing and other objects, advantages and features of theinvention will be more readily apparent from the following description of a preferred embodiment having reference to the drawings, wherein:

Figure 1 is a view in side elevation of an internal combustion engine incorporating a protective device embodying the invention;

Figure 2 is an enlarged fragmentary view similar to a portion of Figure l with parts :broken away and in H section to show certain features of the protective device; Figure 3 is an enlarged fragmentary view similar to a second portion of Figure 1. with parts broken away and in section to show an oilpressure release means incorporatingeertain features of the invention as applied to the illustrative embodiment; and

. Figure 4' is a graph showing the relationship between normal engine oil pressure, minimum safe oil pressure, and the actuating oil -'pressureforthe protective device as related to engine speed.

While the inventionis shown and described as applied to internal combustion engines, such is to be taken only for purposes of illustration since the invention is considered equally applicable to engines of various types.

Referring now. in .detail'to the drawings and more particularly .to Figure 1, thenumeral 10 indicates generally an internal combustion engine adapted to drive a suitable load device, not shown. Air forsupporting' engine combustion istaken in through anair filter 11 which is connect'ed'to' the engine blower 1-2'bya duct-13. Theengine exhaust gas outlet duct is shown at14I Engine-coolant 2,894,502 Patented July 14,

is circulated through the engine and a coolant radiator. 15 by a suitable pump 16; the water outlet of the engine being connected to the radiator by a pipe 17 and a return pipe 18 connecting the radiator to the pump inlet. The numerals 20 and 20' indicate generally the engine protective device and the oil pressure release mechanism, respectively. In the particular engine shown, the blower, coolant pump and the oil pressure pump, not shown, are each driven by the engine. However, it will be appreciated that any of these engine accessories may be separately operated units within the scope of the invention.

As shown in Figure 2, the protective device 20 includes a valve 21 operative to control the flow of combustion supporting air through the air inlet duct 13; valve 21 being of the butterfly type and having a shaft 22 extending into a housing 23 mounted adjacent the duct 13. Fixed onthe shaft 22 within the housing 23 is a member controlling this valve in the form of a lever 24. Yieldable biasing means shown in the form of a torsion spring 26 wrapped around the shaft 22 and having its opposite ends engaging the housing 23 and the lever 24 serves to move the valve from its open position shown to a closed position within the duct 13. Rotatably mounted Within the housing 23 is a latch 27 which is yieldably biased in the counterclockwise direction as viewed in Figure 2 by a second torsion spring 28 for engagement with a keeper such as the pin 29 carried by the lever 24.

The latch 27 has a pair of oppositely extending arms 31 and 32, and having one-way driving connections with these arms for independently effecting opposite or clockwise rotation of the latch against the force of the second spring 28 are a pair of links 33 and 34, respectively. The link 33 has its upper end suitably anchored and sealed to the movable upper end of a bellows element 36 whose lower end is sealed to the open end of a cup-shaped container 35 fixedly mounted on the housing 23. Yieldable biasing means, shown in the form of a coil spring 37 compressed between an adjustable retainer washer 38 threadedly engaging the link 33 and a stationary guide member 39, tends to prevent the bellows from contracting and moving the link 33 downwardly in driving relation with its associated latch arm 31. Similarly, the link 34 has its upper end anchored and sealed to the movable upper end of a second bellows element 40 whose lower end is sealed to the open end of an adjacent cup-shaped container 45 which is likewisefixedly mounted on the housing 23. Yieldable biasing means in the form of a coil spring 41 compressed between the movable upper end of this bellows element and an adjustable retainer nut 42 threadedly mounted in the housing 23 tends to expand the bellows element 40 and move the link 34 upwardly in driving relation with its associated latch arm 32.

The interior of the container 35 surrounding the bellows element 36 is filled with a fluid under subatmospheric pressure having a high rate of thermal expansion and is connected by a sealed conduit 46 to a thermal bulb unit 47 mounted in a coolant conduit 48 extending through the exhaust gas duct 14; both the conduit 46 and the bulb 47 similarly containing such fluid. The conduit 48 is connected at one end to the water outlet end 44 of the engine cylinder head and at its opposite end to the inlet side of the coolant pump housing 16. Since coolant is normally circulated at all times through the conduit 48 during engine operation, the bulb 47 is prevented from being overheated by the exhaust gases flowing over the external surface of the coolant conduit 48. However, in the event that a failure of the coolant circulation system occurs, the coolant within the conduit 48 becomes rapidly overheated and in turn raises the temperature of the thermally expansive fluid in the bulb 47 and conduit 46. The consequent pressure increase in the fluid within .pres l TC of the engine.

the container 35 forces the bellows 36 to contract in opposition to the spring 37 and thus actuates the arm 31 of the latch 27 through link 33 to rotate the latch clockwise thereby disengaging the keeper 2 9 on the valve control lever.

The container 45 is normally subjected to engine lubricatingpressure, being supplied with engine oil througha passageway from the pressure side of the engine lubricating system. This passageway includes a pipe 50 connecting the main oil gallery of the engine, not shown, with .a pipe 51 through a flow restricting orifice 49. The pipe-51 is connected at one end to the container 45 and,.as shownin Figure 3, is connected at its other end to a passage 52 formed in a housing member 53 of the pressure release mechanism 20'. During normal operation of the engine lubricating system, the oil Within the pipe 51 is at sufficient pressure to maintain thebellows 40 contracted with the result that its latch actuating link 34 is prevented frombeingmoved upwardly by its spring 37 to rotate the latch to its disengaged position. However, upon a failure of. the engine oil pump to maintain a minimum predetermined bellows trip pressure in the pipe S1,.the bellows 40 expands under the biasing force of thespring 37 thus raising the link 34 and actuating the latch 27 to its released position.

As;shown in Figure 3, the governor housing member 53 providesa chamber for a centrifugal governor mechanism indicated generally at 54. The housing member 53 has a tubular extension telescopically embraced by a mounting bore provided in the blower housing and has a. bore 57 extending axially therethrough which intersects the passage 52 and rotatably mounts a hollow shaft portion 55 of a flyball or centrifugal weight carrier 56. The weightcarrier 56 is adapted to be driven by an engine-driven shaft,-not shown, such as a shaft of the blower through a flexible shaft connection shown at 53. The hollow shaft portion provides a rotatable valve body havinga central bore .60 and one or more radialports 59 connecting with an annular groove 61 which is formed externally thereon and opens on the passage 52. The bore 60 is also in communication with the interior of the blower housing through one or more radial ports 62 longitudinally spaced from the ports 59 and apassager63.formed between the tubular extension of the housing 53 and the blower end of the carrier 56.

Theweight carrier 56 of the governor mechanism has one or more centrifugal weights .64 pivotally mounted thereon .at 65. Upon speedresponsive outward movement of the weights 64, arms 66 on these weights are arranged to engage one race of .an antifriction bearing indicated at 67 which is suitably mounted on a valve member 67. .The valve member .67 is reciprocably mounted in the valve bore 60, and normally forms a closure for theports 59. Biasing means in the form of a compression spring 68 is seated at one end against the valve member 67 and tends to maintain the valve in its .closed position with respect .to the ports 59in opposition to the'thrustimposed on the valve member bythe speed-responsive outward swinging of the weights during engine operationwhich .varies as the square of the engine pee The -end of the compression spring .68 opposite the valve member 67 extends through a spring-guiding opening169 provided in av cylinder member 70 formingqone end ofthe-chamber'for the flyball mechanism and is seated against a piston member 71 reciprocably-mounted in the cylinder member. The opposite end of the cylinder member is closed by a cap or head member 72 to form an expansible chamber 73 which is connected to the main lubrication gallery of the engine by the pipe 50 thus subjecting the piston member to the lubrication Biasing means in the form of compression spring. 74 is interposed. between piston member 71 and. anannular shoulder formed by the endcf the cylinder member adjacent the opening 69 and tends to bias the piston in opposition to the lubricant pressure applied thereto. It will thus be seen that the position of the piston is determined by a balance between the parallel biasing forces of the springs 68 and 74 and the force of the engine gallery oil pressure acting on the expansible chamber :facingend of the piston member 71. This results in .a.modulation of the biasing action of the spring 68 in accordance with engine oil pressure and consequently in the engiuespeed at which the;ce ntrifugal weights. 6.4. are efiectiveto shiftthevalve member 67 to-open the ports 59.

As shown graphically in Figure .4, the engine oil pressure in conventional engines of this type normally increases as a.substantiallystraight-linefunction of the engine speed and is substantially in excess of the minimum safe oil pressure required to properly lubricate the enginewhich also increases as a substantially straight-line function of the engine speed.

By using the piston spring "L4 in the preferred emlbodiment of the invention and proportioning the relative deflection rates of the springs 68 and 74 so thatthe piston spring absorbs a substantially greater portion of the total force developed by theoil pressure acting on the piston than that portion of such total force absorbed by the speeder spring, the parabolic deviation with increasing engine speed from the desired straight-line function corresponding to the minimum safe oil pressure is reduced to a value within the accepted operating tolerances for such governor mechanisms since the variation in the speeder spring bias dueto h centrifugal forces acting on the weights. is reduced to a relatively insignificant percentage of the total forces involved.

The engine oil pressure as applied to the piston .71 normally maintains the compression spring 68 under sufficient compression to prevent the weights 64 from shifting the valve member 67 a sufficient distance. to uncover the pressure release ports 59 Whenthe engine is operating within its normal speed range. However, should the oil pressure supplied to the chamber 73 fall below-the minimum safe oil, pressure for a particular speed Within the normal. engine ,speed range, the consequent reduced biasing action of the speeder spring 68 permits sufficient outward movement of the fiyweights 64 to shift the valve member to uncover the ports 59 thus connecting the pipe 51 to the interior ofthe {blower housingwhich forms a portion of the oil Collection and return system of the engine. Under such valve open conditions, the oilpressure in pipe 51 and in the container 45 surrounding bellows 40 is relievedbelow the trip pressure for the bellows 40, the flow of oil into the pipe 5 1 being sufficiently restricted by the orifice 49. The-resultant actuation of the rod 34 by the spring 41 disengages latch 27 from its keeper onthe lever member 24controlling the engine intake valve, 21.

The, pressure release mechanism 20' is. similarlyoperative to, relieve the oil pressu e in the pipe 51 and container 45 when the speed of the engine is in excess of a predetermined maximum limited as established by the setting of a nut one stud 76 projecting axially ot the piston. As the engine approaches its maximum speed limit, the -oil pressure supplied to the chamber 73 shifts the piston 71 to bringthe nut ,75 into abutment with a perforated plate 77 interposed between the cylindermember 70 and the end cap 72. Such abutment limits the maximum compression of the speeder spring 68 and thus the mum engine S e d e ond wh ch th flyweights are effective to open the pressure release ports 59 irrespective ,Of the fact that the engine oil pressure lubricating s te ma b c ionin r rly- The minimum speed at which the pressure release mec an sm. is efle t v t ol t e oil Pr su i P 51 el wth l o ,tr pp essu e is ta lis e bi th settin ofla c w whi sth ead bl mount d i e en sap 72 .10 rm an adjus ab abutmen .ts .th lsii or the isistes-aifiea stair-'16. wiimpm erl adjusted,

the screw 78 insures that the Compression spring 68 will maintained underlsuflicient compression to prevent the weightsj64 from shifting the valve member 67 a sufficient distance to: uncover the pressure release ports 59 when the engine is operatng below a predetermined speed A'which may be at o'r slightly 'aboveits normal idle speed.

' Upon the latch 27 beng disengaged from the lever 24, either by reason of the contraction of the bellows 36 in response manure of the coolant system or by reason of the expansion'of the bellows 40 in response to reduced oil pressuresupplied to it from the engine lubricating system, the torsion spring 26 rotates the lever 24, shaft 22 and valve 21 in their counterclockwise direction to stop the flow of air to theengine blower. Consequentially, the engine will automatically'come to a stop.

' Before the engine may be restarted the lever 24 must be returned to its inital position shown and held in such positon until the engne oil pressure within the pipe 51 and the coolant .temperature in the conduit 48 return to normal. For this purpose, as shown in Figure l, the lever 24,is 'provded with" a lost-motion connection indicated at 82 withalever actuating rod 81 which is'provided at its opposite end with'a handle portion 83 accessible for manual operationjjat one end of the engine. Because of thefact'thatthe coolant conduit 48 is in direct heat conductive relation with the engine exhaust gases, and since the oil pressure in the pipe 51 is normally sensitive to the engine oil pump. delivered pressure, the latch actuating links 33 and 34 will promptly return to their normal position, as shown, soon after the engine commences firing thus permittingthelatch27 to be rotated by the spring 28 to re-engage the lever keeper 29 and thereby maintain the valve 21 in its open position.

' ,The operating handle and control rod 81 are also employed to control the engine starter, not shown, the latter being provided with a controller indicated at 84 (Figure 2) in the form of a button for the starter switch 86. The lever 24 is'provided with a surface 87 which is directly opposite the button 84 and spaced slightly therefrom when the lever is in its normal position corresponding to the open position of the'air valve 21. Upon movement of the lever 24 in the resetting direction (clockwise, as in Figure 2) 'to a position slightly beyond the full open position of the valve 21 this surface 87 on the lever engages and moves the starter switch button 84 inwardly to its starter operating position. After the engine commences firing, the handle 83 may be allowed to return a sufiicient distance to effect its disengagement with the starter button, and after it is determined that the latch 27 is engaged the handle may then be fully released, completing the engine start.

'While the invention has been described and shown with reference. to a single illustrative engine installation, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing fromthescope of the invention as defined in the following claims. l

' 1. In combination with an internal combustion engine having an engine combustion air supply duct, an engine oil pressure lubricating system, a valve in said air supply duct normally stopping the flow of air therethrough but movable to an. open position permitting such flow, a member movable with said valve, a latch engageable with said member to hold said member in its valve open'position and movable into and out of latchable relation with said member, and latch actuating means including a first pressure responsive means operative in reponse to engine oil pressure supplied thereto to move said latch out of latchable relation with said member and biasing means yieldably opposing said pressure-responsive means; the improvement comprising oil passage means including a flow restricting orifice-for conducting oil to said first pressure 6. responsive means from the'engineoil pressure lubrication system, said passage means having a pressure relieving opening therein intermediate said orifice and said first pressure responsive means, a closure for said opening, yieldable means biasing said closure to its closed position, means operable in response to engine speed for opening said closure in opposition to said yieldable biasing means, and a second pressure responsive means operable in response to engine oil pressure supplied thereto by said passage means from the pressure supply side of said orifice to modulate the biasing action of said yieldable means and thereby the engine speed at which said engine speed responsive means is operable to open said closure in accordance with engine oil pressure.

2. In combination with a protective device for an engine having an oil pressure lubricating system, a first pressure responsive means operable to signal a failure in said engine oil pressure system, oil passage means for conducting oil to said first pressure responsive means from the engine oil pressure lubrication system, said passage means having a pressure relieving opening, a closure for said opening, yieldable means biasing said closure to its closed position, and means operable in response to excess engine speed for opening-said closure in opposition to said yieldable biasing means thereby simulating a failure in said oil pressure system'and actuating said first pressure responsive means to signal such a failure; a second pressure responsive means voperable to modify the biasing action ofsaid yieldable means in accordance with the engine oil pressure suppliedthereto by said passage means thereby modifying the engine speed at which said speed responsive means is operable to open said closure.

3. A- protective devicefor an engine having a plurality of operating accessory systems, said device including a means'respons'ive to the operating condition of one of said engine accessorysystems and operable to indicate a failure of said-one accessory system, means operable in response to engine speed-to simulate a failure of said one accessory system whereby said first-mentioned means is rendered operable to indicate a'failure of said accessory system, yieldable biasing means opposing the engine speed response of said second means, and a second means responsive to the operating condition of said one accessory system and operable to modify the biasing action of said yieldable means thereby modifying the engine speed at which said speed responsive means is operable to simulate a failure of saidone system in accordance with the operating condition of said one system.

4. In combination with an internal combustion engine having an oil pressure lubricating system and a combustion air supply duct, a valve in said duct normally stopping the flow of air therethrough but movable to an open position permitting such flow, valve controlling means including a member movable with said valve, a latch engageable with said member to hold said member in the valve open position and movable into and out of latchable relation with said member, a latch actuating :memher-movable to the latching position by oil pressure from said lubricating system, means biasing said actuating member to the unlatching position in opposition to said oil pressure, oil passage means connecting said lubricating system with said actuating member, a pressure relief port in said passage means, a valve controlling said port, and engine speed responsive means drivably urging said last-named valve toward its open position; means responsive to the oil pressure in said lubricating system for normally biasing said port controlling valve to its port-closed position in opposition to said speed responsive means, whereby the engine speed at which said speed responsive means is efiective to open said port controlling valve is modulatedin' accordance with the oil pressure of said lubricating system. i

5. A protective device for an internal combustion engine having a pressure lubricating system, said device comprising, in combinatiom a first pressure responsive meansv operable to control the" supply of at least oneof the components required. for combustion within said. engine, oil passage means interconnecting, said first pres sureresponsivemeansto the engine pressure lubricating system and including aflow restricting. orifice, said passage. means having apressure relieving port intermediate said flow restrictingrorifice and said first pressure respon sive means, a valvecontrollingsaid-port, means-' operable in response to engine speed to: bias said valve towards its open position, and means including-a second pressure responsivemeans operable inresponse to engine oil pressure supplied thereto bysaid. passage means to bias said valve toward its. closed position in opposition to said engine speed responsive means thereby modulating the engine speed at which said engine. speed responsive means is operable to move said valveto its open position.

6. In an enginehaving an oil-pressure lubricating syse term, a protective device includinga first pressure'responsive means operable to shut down: said :engine upon a failure in said engine oil; pressure: system, oil passage means for conducting oil to said .firstpressure responsive means from the engine oil pressure lubrication system, said passage means having; a pressure relieving. port, a valve member controlling said port,.means operablein response toexcess engine speed for. actuating. said valve member towardsits'opened position; and yieldablezme'ans biasing said valve member; toward its. closed position in oppSiti0n' to'said speed'responsive means; said yieldable biasing means-includingaspring'compressibly interposed between said valveiand apiston; a'cylinder recip= rocably mounting said pistonandclosed at itsend remote from said valve member to formi an expansible chamber with said. piston, and: a' secondv oil; passage means for connectingsaid' expansible'rchamber' with the engine oil pressure lubricating.system'whereby saidpiston is shifted to modify the:biasing action ofsaidspring: in accordance with theengine oil pressure appliedithereto thereby 'modi; fying the'engine sp'eedrat which. saidspeed responsive means is operable to opemsai'd valve.

7. In the combination asset forth in claim 6, .said' yield.- able biasing. means including. a second. spring having a substantially higher deflection; rate than said firstmentioned spring, said second: spring-being compressively interposed between said cylinder andsaidpiston to bias said piston inaopposit'ion" to the oil pressure supplied to said expansible chamber.

8. The: combination'as-setforthin claim 6 including means for limiting the -movem'ent .offsaid piston. toward said valve member. and thereby. the maximum biasing action of said spring-.whereby-said speed responsive means is operable to move said valve member to its open position whenwthe' speed of. said engine is in excess of a-predetermined maximum irrespective of the engine oil pressure.

9. Ina centrifugalgovernor:for controlling the operation; of a fluid actuated device, fluid pressure passage means for connecting. said fluid actuated device toa source of fluid pressure and including; a flow restricting means, a pressure.relieving port in said passage means betweenzsaid flow restrictingimeans andsaid fluid actuated device, a valve movablestoi close-zandzope'nzsaid pressure relieving port to: the flow ofifluid, .a rotatively driven flyweight movable centrifugallyi-n'response to its increased rotating speed and having a connection with the valve operative to'open the valvein response to centrifugal movement of said weight, means thrustably' biasing the valve closed andyieldably opposing its opening movement by the flyweight, a fluidpressure responsive member providing thrust reaction for said biasingmeans and movable by fluid pressure in adirection to increase the thrust imposed on said valve by said biasing means, saidpressure responsive member being in fluid communication with said passage meansrabove said flow restricting means whereby the rotativespeed atwhich said flyweight is effective. to open. said. valve is increased in. accordance with the supplied-fluidpressuret- I 10. The combination. set forthin. claim 9 and includ ing other biasing means urging. said pressure responsive. member in opposition .to. thefl'uid pressure acting thereon, said other biasingameans being effective to absorb a substantially greater portion of: the fluid pressure forces acting on said pressure responsive member than that portion of suchforces. absorbed. by said first named biasing I11BI1S.

ll. The-combination setforth inclaim-9 and includ-' ing means including a stop limiting, the movement of said pressure responsive member. in a direction to increase the thrust imposed on said'valve by said valve' biasingmeans thereby. establishing. a maximum thrust on said. valve member corresponding. to a predetermined maximum speed beyondrwhiclisaid flyweight is elfective to open said. valve irrespective of" the supplied fluid pressure.

12. In a centrifugal. governor having .a fluid pressure delivery passage'therein, saidI passage having a pressure relieving; porttherein and .a flow restricting orifice above said. port,- a: valve movableto openandzclose said 'port to controlthe How of. fluid-I therethrough, a speeder spring tendingstov bias the valve. to close said port, centrifugal flyweight means: arrangedito opensaidvalve in opposition to saidspeeder spring, ,.a piston supportingthe. end of said speeder spring. opposite .said walveand'means for moving the pistoninopposite directions to increase and'decreasethe valve closing force ofthespeeder' spring, said means including an operatingcylindenforthe piston? in communication withthe passage above said'flow restricting orifice, and asecond s'pringof greater stiffness than the speeder spring urging the piston against the force of the fluid'pressure acting on the piston,- whereby, theb'iasing action. ofsaid speed'er, spring; tending to close the valve is-modified'in accordance with the delivered fluid pressure thereby modulating. th'e speed at which said flyweightmeans is effective to open said valve.

13. In a pressure fluid flow controlling device, PISS-1 sure fluid passage means, a.-flowrestricting means associated-with said passage means, a valve movable to open and close said passage means .to thefi'ow of'fl'uid downstream of said'flow restricting means,;a valve shifting member movable in oppositedifections and having a connection with. the valve operative during movementof said shifting member in one direction to open the valve, resilient means biasing said' valve closed and acting through said'connection to urge said lshifting member-in the other ofsaidl opposite d'ire'ct'rons,,a fluid" pressure responsive member providing} a reaction for said resilient means andv movable by fluid-pressure in a direction to increase the biasing force of said resilient means, said pressure responsive member being in fluid cornmunication witfi said passage means upstream of said. flow restricting means, and other resilient: means biasing .said-i fluid pressure responsive member in..a direction to decrease the biasing force of" said. first namedresilientmeans, said other resilient means having a substantiallyhigherrdeflecw tion rate than said first named resilient means thereby being effective to absorb. a substantially, greater portion of the fluid pressure frcesapplied to said pressure responsive forces than that portionoffsuch forces absorbed by said. first-namedresilient means; and said other resilient means and said pressure responsive .means coact ing .to. modulate .thebiasing. action. of said' first-named .resilient means. onsaid.-valveinaccordance with the sup.- plied .fluid. pressure.

14. A protective. device for an engine havinga pressure lubricating system comprising, in. combination, afirst pressure responsive meansv operable to. control'the fl'ow ofa motive fluid .to said engine, passage means'interconnecting said firstpressureresponsivemeans to theengine pressure lubricating systemand including aflow restricting IifiW: il first pressure-responsive'means being op.-

erable in response to a drop in said lubricating pressure intermediate said flow restricting orifice and said first pressure responsive means below a predetermined pressure to shut off the flow of said motive fluid to the engine, said passage means having a pressure relieving port intermediate said flow restricting orifice and said first pressure responsive means, a valve controlling said port, a first biasing means operable in response to engine speed to bias said valve towards its open position, a second biasing means urging said valve toward its closed position in opposition to said engine speed responsive means, a second pressure responsive means operable to modulate the biasing action of said biasing means and thereby the engine speed at which said engine speed responsive first biasing means is operable to move said valve to its open position in accordance with the engine oil pressure, and means for limiting the modulating action of said second pressure responsive means.

15. In an engine having a pressure lubricating system, a protective device comprising, in combination, a first pressure responsive means operable in response to drop in lubricating pressure in said lubricating system below a predetermined pressure to stop the flow of a motive fluid to said engine, oil passage means interconnecting said first pressure responsive means to the engine pressure lubricating system and including a flow restricting orifice, said passage means having a pressure relieving port intermediate said flow restricting orifice and said first pressure responsive means, a valve controlling said port, centrifugal governor means including a flyweight operable to open said valve in opposition to a speeder spring tending to close the valve, a piston supporting the end of said speeder spring opposite said valve, and means for moving the piston in opposite directions to increase and decrease the valve closing force of the speeder spring, said means including an operating cylinder for the piston in communication with said passage means above said flow restricting orifice, a second spring of greater stiffness than the speeder spring urging the piston against the force of the fluid pressure acting on the piston thereby modifying the valve closing force of the speeder spring and thereby the engine speed at which said flyweight is effective to open said valve substantially in accordance with the fluid pressure acting on said piston, and a stop limiting movement of the piston in its direction increasing the speeder spring force thereby establishing a maximum engine speed beyond which said flyweight is effective to open said valve irrespective of any further increase in engine lubricating pressure.

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